Actually it wouldn't, since the Promise box has been measured capable of sustaining 600MB/s rate in RAID5, 200MB/s over the specified real throughput of the USB3 port.
What is the difference between having three combo TB/USB ports + one mDP port and having three combo TB/mDP ports + one USB port?
In both cases you only have two kinds of ports, could use USB 3 without a dongle or a hub.
Don't be fooled by the current ratio of mDP/TB combo ports to USB ports, this is already shifting with the iMac.
Of course, much more likely is two mDP/TB combo ports and two USB ports (as USB devices will be around in great number for a long time).
Think of it, would you rather have a MBA with one USB3/TB combo port plus one mDP port or one USB3 port plus one mDP/TB combo port?
- One display + one USB device -> both configurations are fine
- One display + Ethernet -> both configurations are fine (though both need a dongle)
- One USB device + Ethernet -> suddenly the USB3/TB solution looks bad (I don't know whether the USB-Ethernet dongle works via a USB hub with the hub still being able to serve other USB devices)
- One USB device + one TB device (external disk, video camera) -> again, the USB3/TB solution needs a hub
Ok,
usb3 isn't as fast as TB with the new Promise box, but for 99,9% of mbp buyers that doesn't matter.
Usb3 is fast enough "for the rest of us" and it's 10x cheaper.
And since if macs would have usb3, almost nobody would need TB and it would be very hard to use it as selling point and that's why Apple might neglect usb3 same way as blu-ray.
Apple is sending very mixed signals about caring their "pro" customers.
Looks like they are dropping pro software little by little and also pro hardware.
Then why should they care about "pro" mbp users?
And at the same time that 0,1% of mbp users that would actually benefit the speed increase of TB over usb3, maybe half of those would also need full bandwidth DP and don't get it.
Oh well, maybe those people have money and will to buy new mac every year and next model will have faster DP in TB as the new displays arrives.
The technical problem in putting DP in LP is that "TB-crippled" DP has only 10 Gbps, which isn't even enough for last gen DP specs, let alone the next one.
This means that once again macs miss a great change for future expandability, which is of course okay for Apple, since people will have to buy new macs sooner and also people don't know that, so they can't blame Apple for it.
About port implementation in MBA:
They could put 2 usb3+TB ports and one mDP.
This would remove the need for dongles for most of the users.
If there is some insane design rule to have only 2 ports, which would be usb3+TB & mDP, you could handle most cases with one TB-hub with some usb3 ports in it.